PayPal's strict requirements for merchants that sell file-storage services have created an opportunity for competitors including BitPay, which processes payments in the digital currency Bitcoin. Last week, four vendors that market the cloud-storage services of Mega — the new venture from controversial Internet entrepreneur Kim Dotcom — stopped accepting payments through PayPal. It is unclear whether PayPal dropped them or vice versa. PayPal, a unit of eBay (NASDAQ: EBAY), allows such merchants to sell only file-sharing services it has approved. PayPal also makes these merchants monitor uploads to prevent copyright infringement — somewhat akin to banks monitoring transactions under anti-money laundering regulations. Stop File Lockers and other antipiracy groups have accused Mega of facilitating illegal downloads. Its founder, Dotcom, faces extradition to the United States f...